Transformer with magnetic leakage shield



y 8, 1963 F. c. OWEN 3,091,744

TRANSFORMER WITH MAGNETIC LEAKAGE SHIELD Filed March 16, 1962 3Sheets-Sheet 1 a1 2135 H615. 20 3o INVENTOR. 5 Freaen'ck C. Owe 7 q, l 2ATTOR/VZ May 28, 1963 F. c. OWEN 3,091,744

TRANSFORMER WITH MAGNETIC LEAKAGE SHIELD Filed March 16, 1962 5Sheets-Sheet 2 1 FIG. 6

L f 47 2 25 44 31 33 .nnnnnn 7 L- /30 A? I l7 INVENTOR.

Frederick C. Owen BY @7 v @mu? ATTORNEY y 8, 1963 F. c. OWEN 3,091,744

TRANSFORMER WITH MAGNETIC LEAKAGE SHIELD Filed March 16, 1962 3Sheets-Sheet 3 1:33 INVENTOR. Freder/ck C. Owe/7 3,091,744 TRANSFGRMERWITH h iAGNETHC LEAKAGE SHIELD Frederick C. Owen, 206 Fenton Place,Charlotte, N11. Filed Mar. 16, 1962, Ser. No. 180,257 12 Claims. (Cl.336--87) My invention relates broadly to transformers and moreparticularly to high magnetic leakage-type transformers having magneticleakage shields.

One of the objects of the invention is to provide shielding means forhigh magnetic leakage-type transformers to enable the same to be encasedwithin a metal container.

Another object of the invention is to provide a construction of highmagnetic leakage-type transformer in which the magnetic leakage isdiminished and confined, thus enabling such transformers to be used inthe vicinity of other electrical equipment without adversely affectingthe same, a feat heretofore unattainable.

Another object of the invention is to provide a construction of highmagnetic leakage-type transformer in which the magnetic leakage flux isconserved and utilized for varying the transformer output current.

Still another object of the invention is to provide a construction oftransformer with a magnetic leakage shield, in which the shield isprovided with a transformer output current control system.

A further object of the invention is to provide a construction oftransformer with a magnetic leakage shield having flux diverting meansfor varying the transformer output current from maximum to minimum andminimum to maximum with very little effort.

Still a further object of the invention is to provide a construction ofwelding transformer having a magnetic leakage shield with means forvarying the welding transformer output current to affect the welding arcvoltage but which will not affect the open circuit voltage.

Other and further objects of the invention reside in the construction ofand manner of manipulating the hunt device extending intermediate themagnetic leakage shield and core in both the preferred and modifiedforms of the invention as set forth more fully in the specificationhereinafter following by reference to the accompanying drawings, inwhich:

FIG. 1 is a front elevational view of the transformer and magneticleakage shield of the invention;

FIG. 2 is a side elevation view of the magnetic leakage shield andparticularly showing the rack gear shunt adjustment mechanism;

FIG. 3 is a top plan view of the structure of FIGS. 1 and 2;

FIG. 4 is an enlarged sectional view taken substantially along line 4-4.of FIG. 1, with parts broken away to show the manner in which themagnetic shield is secured together;

FIG. 4A is an enlarged cross sectional view taken substantially alongline 4A-4A of FIG. 1 and particularly showing the construction of theoptional second shunt;

FIG. 5 is an enlarged fragmentary cross sectional view takensubstantially along line 5-5 of FIG. 3, and particularly showing theadjustable shunt mechanism;

FIG. 6 is an enlarged fragmentary top plan view similar to FIG. 3 butshowing a modified construction of shunt adjustment mechanism;

FIG.'7 is a fragmentary cross sectional view taken substantially alongline 77' ofFIG. 6;

FIG. 8' is a diagrammatic view of a, transformer and shieldembodying thefeatures of the invention and showing one arrangement of transformer.windings applicable to. the invention;

FIG. 9 is a front elevational' view of a modified form 3,91,?44 PatentedMay 28, 1963 of the invention, particularly showing a modifiedarrangement of adjustable shunt;

FIG. 10 is a fragmentary front elevational view similar to FIG. 9,showing a modified construction of the adjustable shunt of FIG. 9; and

FIG. 11 is a diagrammatic view of the modified structure of theinvention as shown in FIGS. 9 and 10 and showing in electrical schematicone arrangement of transformer windings; applicable to the teachings ofthe invention.

Referring to the form of invention shown in FIGS. 1-8, and particularlyto FIG. 8, wherein one arrangement of transformer winding applicable tothe teachings of the invention has been shown in electrical schematic,the laminated core of the transformer is generally designated by thereference numeral 1. The laminated core structure of conventionalconstruction and consisting of a plurality of stacked laminae ofmagnetic material, secured together with insulated bolts 17 or the like,is generally rectangular in shape having end portions 2 and 3, and acentral portion 4 disposed intermediate the end portions 2 and 3 andspanning the side portions 5 and 6 which respectively connectcorresponding ends of the end portions.

The illustrated arrangement of transformer windings on the variousportions of the transformer core is basically that shown and describedin Patent 2,365,722, issued to me on December 26, 1944, for Tarnsformer,although FIG. 8 illustrates the transformer in a more simplified form.The transformer shown is an electric welding transformer; however it isto be understood that the teachings of the invention are applicable to avariety of different transformers of the high magnetic leakage type,having a variety of winding arrangements, and the arrangement shown inFIG. 8 is only for purposes of illustrating one such form of highmagnetic leakage type transformer to which the teachings of theinvention are applicable.

Primary transformer winding 7 having its input leads connected to aconventional alternating current power source, as indicated, ofapproximately volts or other desired rating, is wound on core endportion 3 while the main secondary windings 8 and 9 are respectivelywound on end portions 3 and 2. An auxiliary secondary Winding indicatedat in is wound on central portion 4 of the core and is provided with aplurality of taps lit which are adapted for selective electricalconnection with the movable tap or plug 12 connected to one end of mainsecondary winding a, while the other end of winding 9 is connected tothe WOIiC 13 in accordance with the usual practice. The secondarytransformer circuit is compelted by connection of the other end ofauxiliary secondary winding it with one end of main secondary winding S,with the opposite end of winding 3 connected to the welding electrodeholder 14. The adjustable tap arrangement of the auxiliary secondarywinding provides convenience in selection of the open circuit voltage,the amperage output of the transformer and the welding arc voltage.

A condenser winding 15 having its extremities connected across a bank ofcapacitors id is wound on core end portion 2 either under or over mainsecondary winding 9. In like manner main secondary winding 8 is woundeither over or under primary winding 7 but for purposes of illustrationthe secondary windings 8 and have been shown wound over primary winding7 and condenser winding 15, respectively. The capacitors 116 function toincrease the power factor of the input current and act to increase ordecrease the frequency of the secondary or welding current, dependingupon the size and number of capacitors employed since they are partof anindependent oscillating circuit consisting of the capacitance and itsexciting winding, and enable the operator to maintain the weldingcurrent are as constant as possible as set forth in greater detail inthe beforementioned Patent 2,365,722. Thus this transformer arrangementproduces an ideal are for vertical, overhead and flat horizontal weldingof all types of metals.

The magnetic leakage shield, indicated generally at 18, and comprised ofa plurality of stacked laminae of magnetic material, such as iron, andhaving substantially the same number of laminae as the transformer core1, is supported in spaced relation about the perimeter of the laminatedtransformer core by means of insulating blocks 19. The magnetic leakageshield is thus generally rectangular in shape having the core of a highmagnetic leakage flux transformer supported interiorly thereof. Angleiron frames 29 and 21 are disposed about the perimeter of the magneticleakage shield in cooperating relation as shown particularly in FIGS. 2,3 and 4 and are connected together by means of insulated bolts 22, orthe like, to securely clamp together the plurality of laminae comprisingthe magnetic leakage shield. As shown, the arms of angle iron frames 20and '21 engage the face and edge portions of the magnetic shield laminaeand are insulated therefrom by means of insulation members 23 and 24which extend around the entire perimeter of the magnetic shieldintermediate the laminae and the angle iron frames. Thus the insulationmembers 23 and 2e and insulation bolts 22 prevent any short circuit ofthe magnetic flux paths within the magnetic leakage flux shieldstructure.

In the preferred form of the invention the top portion of the magneticshield is spaced a greater distance from the top portion of thetransformer core than the other portions of the magnetic shield from thecorresponding portions 2, 3 and 6 of the transformer core.

A magnetic shunt or flux diverter, indicated generally at 25, andconsisting of a plurality of laminae 26 of magnetic material ofsubstantially the same number as provided in the magnetic shieldstructure and transformer structure, securely clamped between guideblocks 27 of insulation material by means of insulated bolts 28 or thelike, is positioned intermediate the magnetic shield 18 and transformercore portion 5, as shown more particularly in FIGS. 1 and 5. The laminae21) of the flux diverter 25 are disposed in alignment with the laminaeof the magnetic shield and transformer core with each laminae havingsubstantially the same Width as central portion 4 of the transformercore. The top portion of magnetic shunt 25 is disposed in slidingengagement with the adjacent bottom portion of the magnetic shield 18and a sheet of insulation material 29 secured to the bottom of themagnetic shunt is disposed in sliding engagement with the top surface ofside portion 5 of the transformer core. Provision for the insulationsheet 29 intermediate the magnetic shunt and the transformer core isnecessary in order to prevent short circuit of the magnetic flux pathsbetween the shield and the core.

The magnetic shunt or fiux diverter 25 is disposed to be selectivelypositioned in a plane normal to the plane of the laminae of the variousmembers such that the laminae 26 of the magnetic shunt may be disposedin alignment with all of the corresponding laminae of the shield andtransformer core, or may be selectively positioned to be disposed inalignment with only a selected number of the laminae of the shield andtransformer core, as shown more particularly in FIG. 5, thus reducingthe area of the magnetic shunt flux path interconnecting the shield andcore. The angle iron frames 20 and 21 are appropriately notched to allowfree movement of the magnetic shunt toward and away from the shield andcore. A pair of guide plates 30 and 31, having rectangular aperturestherethrough, indicated generally at 32, of a size somewhat larger thanthe cross sectional area of the magnetic shunt, are clamped togetheroutwardly of angle iron frame members 20 and 21, respectively, by meansof insulation bolts 33, such that their corresponding apertures aredisposed in registration to form a guide for the magnetic shunt, and aredisposed in guiding engagement with magnetic shunt insulation sheet 29as the shunt is moved in the apertures relative to the guide plates.Support members 34 secured to guide plate 30 by welding, or othersuitable means, extend outwardly therefrom and provide guide member 35on their outward extremity for slidably engaging rack gear 36 securelyconnected to guide block 27 at one end of the magnetic shunt assembly.Gearing, indicated at 37, journaled for rotation on support mem bers 34and selectively controlled by hand knob 38, or other suitable means, isdisposed in meshing engagement with rack gear 36 such that the shunt 25is moved inwardly or outwardly with relation to the guide plates 3% and31 upon turning of hand knob 38.

It is to be understood that the magnetic shunt could just as easily bepositioned at the bottom of the transformer intermediate core sideportion 6 and the magnetic shield. At the bottom of the transformer asecondary or auxiliary shunt is provided as indicated at 39, comprisinga plurality of laminae of magnetic material securely clamped between endmembers 40 of insulation material, thus being of substantially the sameconstruction as the previously described adjustable magnetic shunt 25.The auxiliary magnetic shunt 39 is clamped in place beneath centralportion 4 of the transformer core intermediate side portion 6 and themagnetic shield 18 by means of shunt support plate members 41 clamped infrictional engagement with angle iron frames 20 and 21 by means ofinsulation bolts 42 passing through said support plates, shunt endmembers 40 and the auxiliary shunt laminae, as particularly shown inFIGS. 1 and 4A with the top portion of the auxiliary magnetic shuntdisposed in abutting engagement with the bottom surface of core sideportion 6 and an air gap between the magnetic shield and the bottomsurface of the auxiliary shunt. If tolerances are very close it may benecessary to insert a sheet of insulation material between the auxiliaryshunt and the magnetic shield.

Although I have illustrated the auxiliary shunt 39 as being fixed inposition, this shunt could also be selectively adjustable in a mannersimilar to the main magnetic shunt or flux diverter 25. It is also to beunderstood that this shunt could be completely eliminated thus providingthe structure with only a single magnetic shunt. The fixed magneticshunt 39 is utilized for limiting the maximum current output of thesecondary Welding transformer circuit and although the auxiliary shuntillustrated has been shown to contain substantially the same number oflaminae as the magnetic shield and transformer core, the number oflaminae can be reduced to vary the length of the auxiliary shunt to thusvary the maximum transformer current output. The maximum current outputis increased as the number of laminae of magnetic material are decreasedin the auxiliary shunt assembly. If a sheet of insulation material isinserted between the auxiliary shunt and the magnetic shield thethickness of insulation will also affect the magnetic shunt path andcause an effect on the transformer output current.

Although the theory of operation is not completely known, it has beenfound that through experimentation with the device of the invention, thewelding arc current may be easily varied by the operator from minimum tomaximum and from maximum to minimum by adjustment of the main magneticshunt or flux diverter 25. If an auxiliary shunt 39 is utilized themaximum current is set by this shunt and the welding current can thus bevaried from a minimum to this set maximum by the main shunt 25. Thehighest welding output current in the transformer secondary circuit isexperienced when the magnetic shunt 25 is positioned in its maximumoutwardly adjusted position, as indicated in phantom in FIG. 2, where itforms no coupling flux path between the magnetic shield and thetransformer core. Conversely, the minimum welding current is experiencedwhen the magnetic shunt 25 is positioned at its. other extreme, so thatit lies completely between guide plates 30 and 31, as indicated in fulllines in FIGS, 2 and 3, to form the maximum flux path intermediatemagnetic shield 18 and transformer core 1. As stated, the theory ofoperation is not completely known but the laminated magnetic shield 18apparaently functions somewhat like a transformer core, providing aconfining flux path for the magnetic leakage flux, and thus conservesthe magnetic leakage flux from the high magnetic leakage flux typetransformer. The shield thus reduces the flux leakage from the assembly,enabling the transformer and the shield to be placed within a metal casewithout short circuiting the transformer. By inserting the magneticshunt between the shield and the transformer core the leakage flux isdiverted back to the transformer and provides control for thetransformer output current. By selectively Varying the shunt, thetransformer input current, output or welding arc current, and thewelding arc voltage are varied. However, the manipulation of the shunthas no effect whatsoever on the open circuit voltage of the weldingtransformer, that is, the voltage across the secondary before theelectrode welding arc is struck Thus, by using the teachings of theinvention with the transformer shown in FIG. 8, the open circuit voltagecan be maintained at a minimum for operator safety, and when the weldingarc is struck the arc current can be easily adjusted from maximum tominimum or conversely by means of the adjustable magnetic shunt.Magnetic leakage from transformers of the high magnetic leakage fluxtype causes heat losses and loss of secondary power, and these lossesare diminished by use of the magnetic leakage shield arrangement of theinvention.

A modified construction for adjusting the magnetic shunt or fluxdiverter 25 is shown in FIGS. 6 and 7, where in lieu of a rack andpinion gear arrangement for selec tively adjusting the shuntintermediate the magnetic shield and transformer core, a screw 43 isprovided, journaled for rotation within bracket 44 connected to guideblock 27 of the magnetic shunt, and disposed in screw threadedengagement with guide member 45 supported at the extremites of thesupport members 46 which in turn are secured, in the same manner assupport members 34 in the main form of the invention, to the guide plate30. A crank portion 47, or other suitable means such as a handwheel orthe like, is connected to the outward end of screw member 43, whereuponrotation of the crank 47 causes the adjustable shunt or magnetic fluxdiverter 25 to be selectively positioned in the desired mannerintermediate the magnetic shield and transformer core in the same manneras explained in connection with the preferred form of the invention.

Another modified form of the invention is shown in FIGS. 9-1l whereinthe construction of the magnetic shield 18 clamped within angle ironframe members 20 and '21 is the same as that indicated in the preferredembodiment of the invention with the shield spaced from the perimeter ofthe transformer core 1' by insulation blocks I9 in the manner previouslydescribed. It should be noted that the insulation blocks are disposed tosupport the weight of the transformer core and other clamping means maybe provided for maintaining the core in position Within the magneticshield. In the preferred form of the invention, as shown in FIG. 1,other clamping means are not necessary as the guide plates 30 and 31 andthe shunt support plate members 41 serve as clamping means between thecore and the shield to maintain the transformer core within the shield.

In the modified form of the invention shown in FIGS. 9-l1, I have shownthe adaptation of the modified construction to the same transformerwinding arrangement as shown in the preferred form of the invention withlike reference numerals indicating corresponding components. However,the construction of the transformer core 1 and adjustable magnetic shuntor flux diverter 25 is substantially different. The laminatedtransformer core 1, of generally rectangular shape, is comprised of endportions 48 and 49, bottom portion 50 connecting corresponding ends ofsaid end portions, and top portions 51 and 52 respectively connected tothe opposite ends of end portions 48 and 49, and being separated by anair gap indicated generally at 53 through which passes the adjustablemagnetic shunt 25.

The adjustable magnetic shunt or flux diverter comprises a plurality ofelongated rectangular shaped laminae 54 of magnetic material ofsubstantially the same number and arranged in the same plane as thelaminae of the magnetic shield and transformer core, secured together attheir uppermost ends by means of a properly insulated clamping memberand insulated bolt assembly, indicated generally at 55, with the lowerends of the laminae 54 terminating in the sheet of insulation material56 secured thereto by means of adhesive or other suitable means. Thetransformer auxiliary secondary winding 10 is disposed in fixed positionrelative to the transformer and the magnetic shunt 25 is disposedthrough an opening; 57 provided in the top surface of the magneticshield 18 as shown in FIG. 11, through the air gap 53 of transformercore 1 such that it is in sliding engagement with the terminating endsof the core top portions 51 and 52 and extends downwardly through thefixed auxiliary secondary transformer winding 10 with the insulationsheet 56 contacting bottom portion 50 when the magnetic shunt is in itslowermost position as indicated in full lines in FIGS. 9-11. The opening57 in the magnetic shield 18 is of sufiiciently larger size than thecross sectional area of the magnetic shunt so that no contact whateveris made between the magnetic shunt 25' and magnetic flux leakage shield18, to thus eliminate the possibility of short circuiting of themagnetic flux paths between the shield and core. Depending uponmanufacturing tolerances it may be necessary to provide an insulationgasket around the edges of opening 57 A supporting tower arrangement,comprised of angle members 58 connected to the top surface of angle ironframes 20 and 21, by welding or other suitable means, extends upwardlyfrom the top surfaces thereof terminating in a guide member 59 ofelectrical insulation material. The supporting tower arrangementsupports the adjusting mechanism for the magnetic shunt to enable it tobe selectively raised and lowered, with the lowermost position of theshunt being shown in full lines in the various views and the partlyraised position of the shunt being shown in phantom in FIG. 10. It is tobe understood that in the uppermost position the end of the shunt 25 ispositioned flush with the bottom edge of magnetic shield 18 so there, isan air gap between the bottom of the shunt and the transformer core. Inthis fully raised position, the secondary output current or welding arcis at its maximum with the minimum welding current being provided whenthe shunt is in its lowermost position.

As with the preferred form of the invention, various means can beprovided for raising and lowering the magnetic shunt or flux diverter25', and in FIG. 9 I have shown an arrangement of crank and screw 43,44' and 47', which operates in the same manner as the crank and screwmechanism of FIGS. 6 and 7, and in FIG. 10 I have shown an arrangementof rack and pinion gearing 36' and 37, which operates in a mannersimilar to the gearing of FIG. 5, for selectively raising and loweringthe adjust-able shunt to obtain the desired secondary output current forthe welding process.

It should be understood that an auxiliary shunt 39. as described withthe preferred form of the invention, can also be used with this modifiedstructure if it is desired to limit the maximum output current to acertain value. Raising and lowering the shunt 25', of the form of theinvention shown in FIGS. 9-11, cause the transformer output current tovary in the same manner as experienced with corresponding adjustments ofthe shunt 25 in the preferred form of the invention, by diverting thetrans former magnetic leakage flux back to the transformer core, thuscoupling the flux with the transformer windings, and it thereforeappears that the theories of 'operation for both forms are substantiallythe same.

While I have described my invention in certain of its preferredembodiments, I realize that modifications may be made, and I desire thatit be understood that no limitations upon my invention are intendedother than may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

1. A transformer comprising, a core member, inductively relatedtransformer windings wound on said core member, magnetic leakage fluxshield means disposed about the perimeter of said core member in spacedrelation, and separate means connected intermediate said core member andsaid shield means for forming a magnetic flux path between said shieldand said core member and setting the transformer output current.

2. A transformer as set forth in claim 1 in which a gap is provided inthe magnetic flux path intermediate said separate means and said coremember.

3. A transformer as set forth in claim 1 in which a gap is provided inthe magnetic flux path intermediate said separate means and saidmagnetic leakage flux shield means.

4. In combination with a transformer having a primary and secondary,magnetic leakage flux shield means supported in spaced relation aboutthe perimeter of the transformer to confine the magnetic leakage fluxfield, and flux diverter means connected intermediate the shield meansand transformer for selectively setting the trans former output currentwhen the secondary is under load.

5. In combination with a transformer having an inductively relatedprimary and secondary, magnetic leakage flux shield means supported inspaced relation about the perimeter of the transformer forming aconfining flux path for the transformer leakage flux, and flux divertermeans connected for movement intermediate the transformer and shieldmeans and being selectively positionable between two extreme settingsfor varying the transformer output current between a selected minimumand maximum when the secondary is under load.

6. The combination as set forth in claim 5 in which said flux divertermeans is selectively positionable in a plane normal to the plane of thetransformer and shield means.

7. The combination as set forth in claim 5 in which said flux divertermeans is selectively positionable in the plane of the transformer andshield means.

8. The combination as set forth in claim 5 in which maximum transformeroutput current is approached when said flux diverter means is moved froma position intermediate the transformer and shield means.

9. A transformer comprising a core formed with an intermediate leg todivide the core into sections, a primary winding wound on one section ofthe core, a capacity exciting winding wound on the other section of thecore, both of said windings being excluded from said intermediate leg toinductively isolate the two, a secondary winding wound on both sectionsof the core to inductively couple both of the first said windings whenthe secondary is under load, magnetic leakage flux shield meanssupported in spaced relation about the perimeter of said core, and fluxdiverter means connected for movement above the intermediate legintermediate said core and said shield means for selectively varying thesecondary output current when the secondary is under load.

10. A transformer as set forth in claim 9 and a second flux divertermeans beneath the intermediate leg and connected intermediate said coreand said shield means.

11. In combination with a transformer having a normally low power factorand including a primary and secondary, a reactance of a character tomaterially improve the power factor, an energizing winding for thereactance inductively related to the secondary to automatically renderthe reactance effective only when the secondary is under load, magneticleakage flux shield means disposed in spaced relation about theperimeter of the transformer, and selectively adjustable means connectedintermediate the transformer and said shield means for varying theoutput current when the secondary is under load.

12. A transformer comprising a core formed with an air gap on one sidethereof to divide the core into sections, a primary winding wound on onesection of the core, a capacity exciting winding wound on the othersection of the core, a secondary winding wound on both sections of thecore to inductively couple both of the first mentioned windings when thesecondary is under =load, magnetic leakage flux shield means supportedin spaced relation about the perimeter of said core and formed with anaperture in registration with the core air gap, and selectivelyadjustable flux diverter means extending through the aperture of saidshield means and the core air gap and being connected for movementrelative thereto for selectively varying the secondary output currentwhen the secondary is under load.

References Cited in the file of this patent UNITED STATES PATENTS2,311,128 Ranney Feb. 16, 1943 2,555,911 Anderson June 5, 1951 2,671,196Owen Mar. 2, 1954

1. A TRANSFORMER COMPRISING, A CORE MEMBER, INDUCTIVELY RELATEDTRANSFORMER WINDINGS WOUND ON SAID CORE MEMBER, MAGNETIC LEAKAGE FLUXSHIELD MEANS DISPOSED ABOUT THE PERIMETER OF SAID CORE MEMBER IN SPACEDRELATION, AND SEPARATE MEANS CONNECTED INTERMEDIATE SAID CORE MEMBER ANDSAID SHIELD MEANS FOR FORMING A MAGNETIC FLUX PATH BETWEEN SAID SHIELDAND SAID CORE MEMBER AND SETTING THE TRANSFORMER OUTPUT CURRENT.